Which ports do you have open for both TCP and UDP on this machine?
I am a bit concerned that the difference between the two dedicated servers is only one port as the dedicated server uses the port specified for TCP and the +1 for UDP. For example, the default port is 6600. So you would need to forward the ports to 6600 for TCP and 6601 for UDP.
I believe this is the cause of players not being able to see each other.
Edit: Just did some testing on my local server after testing on your server. You definitely do not have the appropriate UDP ports open on your server. I recommend you set your two dedicated servers to ports 6600 and 6602 respectively.
Open your ports in the following fashion:
Thanks for the help I did that and the servers are working A.OK!
I appear to be having a connection time out....